United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
P.O. Box 93478
Las Vegas NV 89193-93478
Pre-issue Copy
October 1987
Research and Development
An Interlaboratory Study
of Inductively Coupled
Plasma Atomic Emission
Spectroscopy Method 6010
and Digestion Method 3050
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PROJECT SUMMARY
AN INTERLABORATORY STUDY OF INDUCTIVELY COUPLED PLASMA
ATOMIC EMISSION SPECTROSCOPY METHOD 6010
AND DIGESTION METHOD 3050
by
Clifton L. Jones, Vernon F. Hodge, Donald M. Schoengold,
Homigol Biesiada, Thomas H. Starks, and Joseph E. Campana
Environmental Research Center
University of Nevada, Las Vegas
Las Vegas, Nevada 89119-9770
Contract Number 68-01-7159
Contract Number 68-01-7253
Technical Monitor
Thomas A. Hinners
Quality Assurance and Methods Development Division
U.S. Environmental Protection Agency
Las Vegas, Nevada 89193-3478
X
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
(v, OFFICE OF RESEARCH AND DEVELOPMENT
Ği U.S. ENVIRONMENTAL PROTECTION AGENCY
x LAS VEGAS, NEVADA 89193-3478
O
^ MAY 1987
o
-------
NOTICE
The information in this document has been funded wholly or
in part by the United States Environmental Protection Agency
under Contract Number 68-01-7159 to the University of Nevada,
Las Vegas, Nevada, and under Contract Number 68-01-7253 to Viar
and Company, Alexandria, Virginia. It has been subject to the
Agency's peer and administrative review, and it has been
approved for publication as an EPA document.
11
-------
ABSTRACT
The design, execution, and results of an interlaboratory
study of Method 6010, "Inductively Coupled Plasma Atomic
Emission Spectroscopy," are described. This study examined the
application of the method to the analysis of solid-waste
materials for 23 elements. Part of the interlaboratory study
included a study of Method 3050, "Acid Digestion of Sediments,
Sludges and Soils," which is integral to Method 6010 when
considering the analysis of certain solid wastes. The overall
study was designed so that the variability of the two methods
was separable. Method performance data, including precision
and accuracy, are presented and discussed. A comparison of the
inductively coupled plasma atomic emission and atomic
absorption spectroscopic techniques is presented, as well as a
comparison of results from two different types of inductively
coupled plasma spectrometers. The limitations of the methods
are described, and suggestions are given to improve the general
application of Method 6010.
iii
-------
ACKNOWLEDGMENTS
Use of the EPA contracts numbered 68-01-7159 and
68-01-7253 for this study was graciously permitted by the
respective project officers, Duane A. Geuder and Michael H.
Carter.
IV
-------
INTRODUCTION
An interlaboratory study of solid wastes using the EPA
analytical Method 6010 entitled "Inductively Coupled Plasma
Atomic Emission Spectroscopy" (ICP-AES), which is included in
the EPA methods publication SW-846, was performed with nine
participating laboratories. This inter laboratory study
concentrated on the application of Method 6010 for the
determination of 23 elements in seven solid materials including
dried sludges, sediments, and fly ash. The 23 target elements
are: Al, Sb, As, Ba, Be, Cd, Ca, Cr, Co, Cu, Fe, K, Pb, Mg,
Mn, Mo, Ni, Se, Ag, Na, Tl, V, and Zn. This study followed a
single-laboratory evaluation that investigated the application
of Method 6010 to a variety of aqueous and solid-waste samples.
The different waste matrices studied in the single-laboratory
evaluation required the utilization of several different
digestion procedures. In contrast, this interlaboratory study
examined Method 6010 for the analysis of solid wastes that were
digested using a single digestion procedure.
Since the digestion of solid samples is necessary to apply
Method 6010 for the analysis of wastes, a thorough study of
-------
Method 6010 must also include digestion as a variable.
Consequently, a parallel study of Method 3050 (Acid Digestion
of Sediments, Sludges, and Soils) was included as an integral
part of the interlaboratory study. The present study was
designed to determine the performance of Method 6010 both
independent of and together with the Method 3050 digestion
procedure.
Seven solid materials, representative of solid wastes,
were selected as the method evaluation materials. Three of the
materials (river sediment, coal fly ash, and estuarine
sediment) are Standard Reference Materials from the National
Bureau of Standards, and one material (the mine tailing) is an
EPA reference material. The other three solids (a contaminated
soil and two" industrial sludges) were obtained from the EPA. A
detailed homogeneity study was performed by the coordinating
laboratory before the solids were distributed to the
participating laboratories. The results indicated that the
solid samples were homogeneous.
Sixteen grams of these homogeneous solids were distributed
to the laboratories to be digested by Method 3050, both
unspiked and spiked. The spiking solutions provided to the
laboratories contained 19 of the 23 target elements. They were
-------
designed to be added to the solids prior to digestion to bring
the concentrations of the 19 elements in the laboratories'
digests to minimum levels of about 100 times the corresponding
"Estimated Instrumental Detection Limits" given in Method 6010.
It was not necessary to spike Al, Ca, Fe, and Mg into the
solids because of the high endogenous concentrations of these
metals in the 7 solid samples. Having each laboratory spike
portions of the solid samples with the spiking solutions prior
to digestion assured that each laboratory used equally spiked
aliquots of the solids. This procedure eliminated the need to
create uniformly spiked solids for distribution. The resulting
digests were analyzed by Method 6010.
In order to remove sample-preparation variability from
measurement variability, bulk digests of the 7 solid samples
were prepared by the coordinating laboratory for distribution
to the participating laboratories. These bulk digests were
spiked with the same spiking solutions that were used to spike
the solid samples. Thus, the spiked bulk digests of the seven
solid samples were very similar in composition to the spiked
solids digests that were prepared by the laboratories.
Therefore, data from the Method 6010 analyses of these spiked
bulk digests could be compared to data from the spiked solids
in order to estimate the variances due to the digestion and
-------
analysis" procedures. In order to test the effects of high
levels of V and Mo on the determination of the other analytes
by Method 6010, the spiked bulk digest from the fly ash solid
was also spiked to contain 0.1 percent of these interfering
elements.
In addition to the solid samples and the spiked bulk
digests, two QC solutions containing the target elements were
provided to the participating laboratories for analysis with
and without digestion. Because these solutions were carefully
prepared and verified by the coordinating laboratory, the
results could be used to estimate the accuracy of the Methods.
Other solutions were provided to the participating laboratories
to insure high ICP-AES data quality. These were initial
calibration verification solutions and an interference check
solution.
The results of this collaborative study yielded
quantitative information on the precision and accuracy of
Method 6010, independently and together with Method 3050. Data
obtained on sequential and simultaneous ICP-AES instruments as
well as by atomic absorption spectroscopy (AAS) were compared
statistically, and the results are reported. The method of
-------
standard additions (MSA) is a conditional requirement of Method
6010, so its effect on data quality was investigated.
RESULTS AND DISCUSSION
This mul t i 1 a bor a t or y evaluation of Method 6010
demonstrates that the method, as described, is capable of
achieving excellent accuracy and precision for the
determination of the 23 elements in quality control (QC)
solutions. These QC solutions contained the 23 elements at
concentrations of approximately 100 times the instrumental
detection limits, and the solutions were interference-free in
that no interfering elements were present at high
concentrations. Accuracy for the multilaboratory analyses of
the QC solutions (when the mean values are expressed as a
percentage of the target values) varies from 95 percent to 104
percent for the solutions analyzed without digestion and varies
from 93 percent to 103 percent (silver excluded) for the
solutions digested before being analyzed. Digestion of the QC
solution containing silver resulted in a mean silver value that
is only 53 percent of the target value whereas the mean silver
value is 100 percent of the target value for the direct
analyses of this QC solution. The percent RSD's for the
-------
elements range from 3.1 percent to 9.1 percent for the QC
solutions that were analyzed by Method 6010 without digestion
and from 2.6 percent to 13 percent (when silver is excluded)
for the QC solutions that were analyzed after digestion by
Method 3050. The median percent RSD's for the 2 sets of QC
solutions are 6.5 and 6.7 percent, respectively. This
precision is considered excellent for these solutions. Silver
with a percent RSD of 52 is the lone outlier in the QC solution
set that was digested before analysis.
The interlaboratory precision for Method 6010, with
digestion eliminated as a variable, was determined for the 23
elements in the spiked bulk digests of six representative solid
complex matrices, including river and estuarine sediments and
industrial sludges (Table 1). The analyte concentrations in
these spiked bulk digests were about 100 times the instrumental
detection limits. The median percent RSD's for the 6 sediments
across 23 elements range from 6.8 percent to 11 percent. Thus,
the precision for the measurement of the target elements in
these complex solutions is very good.
The seventh spiked bulk digest, from coal fly ash, was
spiked with very high levels of molybdenum and vanadium (0.1
percent). The median percent RSD's for the determination of
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TABLE 1. PERCENT RSD's FOR THE DETERMINATION OF THE 23 TARGET ELEMENTS
IN THE SPIKED BULK DIGESTS
ELEMENTS
Al
Sb
AS
Be
Cd
Ca
Cr
Co
Cu
Fe
Pb
Mg
Mn
Mo
Ni
Se
Ag
Tl
V
Zn
Ba
Na
K
MEDIAN
PERCENT
RSD
HAZARDOUS
WASTE 1
11
5.6
13
5.8
11
8.8
6.2
11
4.4
6.6
15
8.8
10
20
9.4
7.5
44
19
12
9.1
11
17
8.8
10
RIVER
SEDIMENT
19
52
11
5.8
6.6
9.4
5.5
14
4.3
8.3
7.2
8.1
13
33
8.9
13
23
13
58
6.7
10
38
7.4
10
FLY
ASH
16
73
83
57
5.7
5.6
36
21
9.7
8.8
22
15
14
19
8.1
16
17
22
7.5
7.6
8.7
49
4.2
16
ESTUARINE
SEDIMENT
1.9
8.7
22
4.8
7.6
5.3
7.6
6.8
6.0
6.0
4.7
9.4
11
28
5.4
6.2
46
29
7.3
15
6.4
4.7
4.8
6.8
INDUSTRIAL
SLUDGE
11
3.2
25
6.4
3.1
8.5
5.8
6.7
11
6.9
3.9
8.0
11
16
5.1
13
47
30
5.5
10
8.0
5.8
13
8.0
ELECTRO-
PLATING
SLUDGE
13
24
8.6
9.9
9.8
7.0
7.8
11
7.8
8.4
5.6
20
9.6
36
9.2
13
19
20
11
2.5
20
9.8
5.8
11
MINE
TAILING
7.6
4.4
5.3
8.5
12
7.9
39
15
12
8.4
8.0
10
5.5
21
12
19
27
29
18
16
11
7.9
7.9
11
-------
the 23 elements in this spiked digest range from 4.2 percent to
83 percent with a median of 16 percent (Table 1). The 12
percent median RSD for fly ash digests without added Mo and V
(Table 2) suggests that these two elements decreased the
measurement precision.of many of the target elements.
When Method 6010 and Method 3050 are applied in
combination for the determination of the 23 elements in spiked
solids, the apparent measurement precision decreases (Table 2)
when compared to the corresponding spiked bulk digest. The
median percent RSD's for the 7 solids across the 23 elements
range from 11-17 percent. The spiked solid samples were spiked
prior to digestion to assure that the concentrations of the
analytes in the resulting digests were approximately 100 times
greater than the instrumental detection limits. The accuracy
of the ICP Method 6010 can be estimated for these complex
matrices by comparing the average concentrations of the
elements in the spiked bulk digests (as determined by Method
6010) to the corresponding concentrations which were determined
by AAS by one of the participating laboratories. A null
hypothesis approach that is based on the mean and on the
corresponding standard deviation was used to determine if the
ICP-AES and AAS values are significantly different at the 95
percent confidence level. The results indicate that only two
8
-------
TABLE 2. PERCENT RSD's FOR THE DETERMINATION OF THE 23 TARGET ELEMENTS
IN THE SPIKED SOLIDS
HAZARDOUS
WASTE 1
ELEMENTS
Al
Sb
As
Be
Cd
Ca
Cr
Co
Cu
Fe
Pb
Mg
Mn
Mo
Ni
Se
Ag
Tl
V
Zn
Ba
Na
K
MEDIAN
PERCENT
RSD
17
27
13
16
13
7.3
7.9
18
12
14
15
5.9
14
19
13
13
19
19
18
14
8.4
14
19
14'
RIVER
SEDIMENT
24
56
26
13
8.
9.
22
22
14
19
6.
8.
9.
31
20
9.
7.
28
19
12
9.
40
17
17
4
0
4
4
0
4
6
8
FLY
ASH
20
25
16
7.6
9.3
12
9.7
12
10
44
9.6
17
11
24
9.7
9.8
50
34
12
11
7.2
32
18
12
ESTOARINE
SEDIMENT
22
62
22
11
14
10
7.1
9.2
9.7
16
11
9.0
10
18
10
10
34
28
10
13
14
9.4
18
11
INDUSTRIAL
SLUDGE
14
28
20
18
19
12
18
18
19
18
20
16
16
18
20
15
30
18
18
20
16
20
22
18
ELECTRO-
PLATING
SLUDGE
18
40
20
7.0
18
14
12
13
9.4
14
19
10
18
43
15
18
27
43
39
8.2
30
15
5.7
18
MINE
TAILING
26
58
22
16
20
12
26
18
12
18
5.8
10
9.4
20
17
12
50
44
24
20
7.2
12
16
18
-------
out of 184 elemental measurements by the two methods are
significantly different. The ICP-AES mean value was
statistically higher than the AAS value for Ca in the digests
of the Estuarine Sediment and the Mine Tailing Waste. In some
cases where the ICP/AAS ratios are very different (less than
0.75 or greater than 1.25), the standard deviations in the ICP
measurements are very high, and, therefore, the differences in
the means are not significant. Overall, the agreement between
ICP and AAS is excellent.
The median percent RSD's for the same 7 solids, unspiked,
range from 17-27 percent (Table 3). This poorer precision when
compared to the spiked solids results because over 50 percent
of the reported concentration values are less than 100 times
the average of the instrumental detection limits. In other
words, as the concentrations approach the instrumental
detection limits the precision decreases as indicated by the
higher percent RSD values. Four elements among those with the
highest median percent RSD's are antimony, selenium, silver and
arsenic. For those elements that were present in the digests
of the unspiked solids at concentrations 100 times greater than
the IDL's (due to their occurrence in high concentrations in
the unspiked solids), the precision is comparable to the
precision for the spiked solid samples.
10
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TABLE 3. PERCENT RSD'S FOR THE DETERMINATION OF THE 23 TARGET ELEMENTS
IN THE UNSPIKED SOLIDS
ELEMENTS
Al
Sb
As
Be
Cd
Ca
Cr
Co
Cu
Fe
Pb
Mg
Mn
Mo
Ni
Se
Ag
Tl
V
Zn
Ba
Na
K
MEDIAN
PERCENT
RSD
HAZARDOUS
WASTE 1
19
38
53
31
37
9.0
11
24
10
13
8.0
6.0
8.6
30
14
42
41
31
21
14
7.4
66
23
21
RIVER
SEDIMENT
32
78
48
27
17
13
19
60
9.4
24
12
11
17
42
25
61
43
30
72
12
11
52
34
27
FLY
ASH
19
32
27
57
10
28
23
16
52
33
20
24
20
34
47
15
20
4.3
34
20
23
ESTUARINE
SEDIMENT
23
18
35
52
11
22
12
17
10
37
10
10
58
21
30
1.4
17
8.6
14
9.1
17
17
INDUSTRIAL
SLUDGE
15
47
83
42
17
10
12
21
17
14
16
18
18
56
16
43
38
38
28
12
24
16
32
18
ELECTRO-
PLATING
SLUDGE
23
68
44
70
22
17
12
46
12
12
17
14
21
49
20
74
54
45
35
9.2
38
17
9.6
22
MINE
TAILING
17
57
28
41
59
8.6
90
30
20
18
17
9.2
11
26
40
77
60
120
47
20
8.8
13
24
26
-------
The Method 6010 variance and the Method 3050 variance can
be calculated from the data base resulting from the analyses of
the spiked bulk digests and the spiked solid samples (Table 4).
A statistical analysis of the data shows that in general, the
digestion procedure and the ICP-AES analytical procedure
contribute about equally to the overall measurement uncertainty
or precision (variance) for the determinations of the 23 target
elements in digests of these 7 homogeneous solids.
The method of standard additions was required for less
than 10 percent of the total analyses. Results by ICP-AES
using the method of standard additions were compared with
non-MSA data for the spiked bulk digest samples. The
comparison of this limited data set (Table 5) indicates that on
the average there is no consistent improvement in the data
quality when the method of standard additions is used with
Method 6010 for the analysis of the solid matrices that were
used in this study.
A comparison between data obtained on simultaneous and
sequential inductively coupled plasma spectrometers indicated
that the concentration values were statistically
indistinguishable.
12
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TABLE 4. ESTIMATED PERCENTAGE CONTRIBUTIONS OF METHOD 6010 ICP
VARIANCE AND METHOD 3050 DIGESTION VARIANCE TO TOTAL VARIANCE
Elements
Al
Cd
Ca
Co
Cu
Fe
Pb
Mg
Mn
Mo
Ni
Se
Tl
Zn
Ba
K
Be
V
Sb
As
Cr
Na
Ag
6010 ICP
41
26
50
39
38
11
66
100
68
100
27
89
63
55
37
22
25
24
3
35
26
25
100
3050 Digestion
59
74
50
61
62
89
34
0
32
0
73
11
37
45
63
76
75
76
97
65
74
75
0
Median: 46 55
13
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TABLE 5. COMPARISON OF MSA AND NON-MSA RESULTS3
SPIKED BULK DIGESTS
NON-MSA
SAMPLE NAME
HAZARDOUS WASTE
HAZARDOUS WASTE
HAZARDOUS WASTE
RIVER SEDIMENT
FLY ASH
FLY ASH
FLY ASH
FLY ASH
FLY ASH
FLY ASH
ESTUARINE SEDIMENT
INDUSTRIAL SLUDGE
ELECTROPLATING SLUDGE
MINE TAILING
ELEMENT
Cd
Tl
Zn
Tl
Cd
Cr
Pb
Mn
Ni
Tl
Tl
Tl
Tl
Cd
N
5
5
5
7
5
5
4
4
3
4
5
5
3
5
MEAN
CONG. SD
894
4410
4310
3160
754
1480
4100
1910
1530
5530
3870
4470
4600
850
117
788
426
2210
422
885
634
233
154
3730
1290
872
740
69
N
3
3
3
3
3
3
4
3
4
3
3
3
4
3
MSA
MEAN
CONC. SD
940
4510
4560
5050
897
2390
6770
1750
1350
1950
3340
4620
5350
985
84
1130
250
675
219
1090
3300
304
500
2470
2850
2230
1120
112
%RATIO
95
98
95
63
84
62
61
109
113
284
116
97
86
86
SIG.
DIF.C
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
Only those elements that required the application of the MSA by three or
more laboratories are included as statistically significant.
Concentration for liquids in ug/L; concentration for solids in rag/kg.
Result of a null hypothesis approach used to indicate whether MSA and non-MSA
results are significantly different.
N - Number of cases.
% Ratio - non-MSA to MSA mean concentrations.
(continued)
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TABLE 5. (continued)
UNSPIKED SOLIDS
SAMPLE NAME ELEMENT
HAZARDOUS WASTE
HAZARDOUS WASTE
HAZARDOUS WASTE
HAZARDOUS WASTE (DUP.)
RIVER SEDIMENT
RIVER SEDIMENT
RIVER SEDIMENT
RIVER SEDIMENT
RIVER SEDIMENT (DUP.)
RIVER SEDIMENT (DUP.)
FLY ASH
MINE TAILING
MINE TAILING
MINE TAILING (DUP.)
MINE TAILING (DUP.)
MINE TAILING (DUP.)
MINE TAILING (DUP.)
ELECTROPLATING SLUDGE
ELECTROPLATING SLUDGE
ELECTROPLATING SLUDGE (DUP.)
ELECTROPLATING SLUDGE (DUP.)
INDUSTRIAL SLUDGE
Be
Cr
Co
Ni
Sb
Cd
Co
Ni
Cd
Ni
Be
Cd
Zn
Cd
Co
Ni
Zn
Cd
Mn
As
Mo
As
N
4
6
6
5
6
6
5
6
6
6
6
4
6
4
6
5
6
6
6
6
5
4
NON-MSA
MEAN
CONG. SD
0.8
95
8.0
17
325
11
21
44
10
39
3.0
2.3
372
2.4
7.3
21
365
113
226
33
14
11
0.1
8.4
2.4
1.3
266
2.5
16
20
1.6
13
0.8
1.6
44
1.6
2.5
5.6
43
24
31
20
11
6.6
N
3
3
3
4
3
3
4
3
3
3
3
3
3
3
3
4
3
3
3
3
3
3
MSA
MEAN
CONG.
0.7
111
9.1
13
169
11
21
27
10
38
2.6
1.9
340
1.5
8.8
21
345
96
254
41
21
26
SD
0.2
10
1.5
8.9
246
3.5
19
7.0
0.7
19
1.2
1.1
119
0.8
3.1
11
122
41
126
20
7.3
11
%RATIO
93
86
88
128
192
103
99
161
107
105
114
122
109
158
83
100
106
118
89
80
68
41
SIG.
DIF.C
NO
YES
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
YES
(Continued)
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TABLE 5. (concluded)
SPIKED SOLIDS
NON-MSA
MEAN .
SAMPLE NAME ELEMENT
HAZARDOUS WASTE
HAZARDOUS WASTE
HAZARDOUS WASTE
HAZARDOUS WASTE
HAZARDOUS WASTE (DUP.)
HAZARDOUS WASTE (DUP.)
HAZARDOUS WASTE (DUP.)
ESTUARINE SEDIMENT
ESTUARINE SEDIMENT
ESTUARINE SEDIMENT
ESTUARINE SEDIMENT
ESTUARINE SEDIMENT (DUP.)
MINE TAILING
MINE TAILING (DUP.)
ELECTROPLATING SLUDGE (DUP.)
Co
Pb
Mo
Ni
Co
Pb
Ni
Cd
MO
Ni
Tl
Ni
Ni
Ni
Tl
N
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
CONG. SD
45
340
39
57
48
390
61
46
37
65
180
63
64
63
160
8.2
104
20
10
4.8
29
3.5
4.7
19
6.7
65
6.9
7.9
6.9
46
N
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
MSA
MEAN
CONC.b
30
238
29
37
56
338
58
53
47
73
239
74
60
64
304
SD %RATIO
2.2
14
2.8
2.9
11
112
14
2.2
2.5
1.3
24
3.3
15
19
104
149
143
134
152
85
115
106
87
79
89
75
86
108
99
53
SIG.
DIF.C
YES
NO
NO
YES
NO
NO
NO
NO
NO
NO
NO
YES
NO
NO
YES
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RECOMMENDATIONS
The experimental design used in this multilaboratory study
has resulted in several excellent sets of multidimensional
analytical data that deserve consideration beyond the intended
scope of this report. Further analysis and interpretation of
this data base is suggested.
The presence of high concentrations (0.1 percent) of added
vanadium and molybdenum in the fly ash spiked bulk digest could
account for the apparent decrease in the precision of Method
6010 for the determination of many of the 23 target elements in
this matrix compared to the 6 other solid digests. The
interfering effects in this matrix should be studied further.
The poor precision, accuracy, and spike recoveries for
silver demonstrated in this study, should .be noted in both
Method 3050 and Method 6010. The possibility of precipitation
in the nitric/hydrochloric acid digestion matrix as well as
phototransformation should be discussed in Method 3050.
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The poor spike recovery of antimony, observed in this
study, should be noted in Method 3050. In particular, the
possibility of the formation of oxide and oxo-chloride
precipitates of antimony in the nitric/hydrochloric acid
digestion matrix should be discussed.
The application of the method of standard additions (MSA),
a conditional requirement of Method 6010, affects the
economics, the turnaround time of analysis, the practicality of
the Method, as well as the data quality. Although this report
indicates that, on the average, MSA data were not consistently
different from non-MSA data, the requirement for the
application of the MSA should be investigated further.
When soil-containing matrices are being analyzed by Method
6010, the authors are of the opinion that the method of
standard additions should not be required for those elements
that are endogenous to soils in high concentrations. The
high-concentration endogenous elements in soils include Al, Ca,
Fe, Mg, K, and Na.
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Information box:
The authors are with the Environmental Research Center,
University of Nevada, Las Vegas, Nevada 89119-9770. Thomas A.
Hinners is with the EPA at EMSL, Las Vegas, Nevada 89193-3478.
The complete report, entitled "An Interlaboratory Study of
Inductively Coupled Plasma Atomic Emission Spectroscopy Method
6010 and Digestion Method 3050," will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, Virginia 22161
Telephone: 703-487-4650
The EPA Technical Monitor under which the work was done
was Thomas A. Hinners. He can be contacted at:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
P.O. Box 93478
Las Vegas, Nevada 89193-3478
Telephone: 702-798-2140
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